gsm29118: add generator functions for GSM29118 messages

We already have some GSM29118 related definitions and functions in
libosmocore. Lets also add some functions to generate GSM29118 messages
(similar to those we have for GSM0808).

Change-Id: Ic87f8a771b87b52215d0a7451b67794557b80b8a
Related: OS#3615

2 files changed, 290 insertions, 0 deletions

diff --git a/src/gsm/gsm29118.c b/src/gsm/gsm29118.c
index 3898be64..ca210fbf 100644
--- a/src/gsm/gsm29118.c
+++ b/src/gsm/gsm29118.c
@@ -1,7 +1,32 @@
+/* (C) 2018 by sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Harald Welte, Philipp Maier
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
 #include <osmocom/core/utils.h>
 #include <osmocom/gsm/tlv.h>
 
 #include <osmocom/gsm/protocol/gsm_29_118.h>
+#include <osmocom/gsm/gsm29118.h>
+#include <osmocom/gsm/apn.h>
+#include <osmocom/gsm/gsm48.h>
 
 const struct value_string sgsap_msg_type_names[] = {
 	{ SGSAP_MSGT_PAGING_REQ,	"PAGING-REQUEST" },
@@ -156,3 +181,253 @@ const struct tlv_definition sgsap_ie_tlvdef = {
 		[SGSAP_IE_TMSI_BASED_NRI_CONT]	= { TLV_TYPE_TLV },
 	},
 };
+
+
+/* Allocate an empty message buffer, suitable to hold a complete SGsAP msg. */
+struct msgb *gsm29118_msgb_alloc(void)
+{
+	/* by far sufficient for the maximum size message of 298 bytes
+	 * (9+7+5+3+10+253+10+1) SGsAP-UP-UD */
+	return msgb_alloc_headroom(1024, 512, "SGsAP");
+}
+
+/* Encode VLR/MME name from string and append to SGsAP msg */
+static int msgb_sgsap_name_put(struct msgb *msg, enum sgsap_iei iei, const char *name)
+{
+	uint8_t buf[APN_MAXLEN];
+	uint8_t len;
+	/* encoding is like DNS names, which is like APN fields */
+	memset(buf, 0, sizeof(buf));
+	len = osmo_apn_from_str(buf, sizeof(buf), name);
+
+	/* Note: While the VLR-Name (see 3GPP TS 29.118, chapter 9.4.22) has
+	 * a flexible length, the MME-Name has a fixed size of 55 octets. (see
+	 * 3GPP TS 29.118, chapter 9.4.13). */
+	if (iei == SGSAP_IE_MME_NAME && len != SGS_MME_NAME_LEN)
+		return -1;
+	msgb_tlv_put(msg, iei, len, buf);
+	return 0;
+}
+
+/* Encode IMSI from string representation and append to SGSaAP msg */
+static void msgb_sgsap_imsi_put(struct msgb *msg, const char *imsi)
+{
+	uint8_t buf[16];
+	uint8_t len;
+	/* encoding is just like TS 04.08 */
+	len = gsm48_generate_mid_from_imsi(buf, imsi);
+	/* skip first two bytes (tag+length) so we can use msgb_tlv_put */
+	msgb_tlv_put(msg, SGSAP_IE_IMSI, len - 2, buf + 2);
+}
+
+/* Encode LAI from struct representation and append to SGSaAP msg */
+static void msgb_sgsap_lai_put(struct msgb *msg, const struct osmo_location_area_id *lai)
+{
+	struct gsm48_loc_area_id lai_enc;
+	gsm48_generate_lai2(&lai_enc, lai);
+	msgb_tlv_put(msg, SGSAP_IE_LAI, sizeof(lai_enc), (uint8_t *) & lai_enc);
+}
+
+/* Many messages consist only of a message type and an imsi */
+static struct msgb *create_simple_msg(enum sgsap_msg_type msg_type, const char *imsi)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, imsi);
+	msgb_push_u8(msg, msg_type);
+	return msg;
+}
+
+/* 8.3 SGsAP-ALERT-REQUEST.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \returns callee-allocated msgb with the encoded message.*/
+struct msgb *gsm29118_create_alert_req(const char *imsi)
+{
+	return create_simple_msg(SGSAP_MSGT_ALERT_REQ, imsi);
+}
+
+/* 8.4 SGsAP-DOWNLINK-UNITDATA.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \param[in] nas_msg user provided message buffer with L3 message.
+ *  \returns callee-allocated msgb with the encoded message. */
+struct msgb *gsm29118_create_dl_ud(const char *imsi, struct msgb *nas_msg)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, imsi);
+	msgb_tlv_put(msg, SGSAP_IE_NAS_MSG_CONTAINER, nas_msg->len, nas_msg->data);
+	msgb_push_u8(msg, SGSAP_MSGT_DL_UD);
+	return msg;
+}
+
+/* 8.5 SGsAP-EPS-DETACH-ACK.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \returns callee-allocated msgb with the encoded message. */
+struct msgb *gsm29118_create_eps_det_ack(const char *imsi)
+{
+	return create_simple_msg(SGSAP_MSGT_EPS_DET_ACK, imsi);
+}
+
+/* 8.7 SGsAP-IMSI-DETACH-ACK.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \returns callee-allocated msgb with the encoded message. */
+struct msgb *gsm29118_create_imsi_det_ack(const char *imsi)
+{
+	return create_simple_msg(SGSAP_MSGT_IMSI_DET_ACK, imsi);
+}
+
+/*! 8.9 SGsAP-LOCATION-UPDATE-ACCEPT.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \param[in] lai Location Area Identity (optional, may be NULL).
+ *  \param[in] new_id value part of new Mobile Identity (optional, may be NULL).
+ *  \param[in] new_id_len length of \a new_id in octets.
+ *  \returns callee-allocated msgb with the encoded message */
+struct msgb *gsm29118_create_lu_ack(const char *imsi, const struct osmo_location_area_id *lai, const uint8_t *new_id,
+				    unsigned int new_id_len)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, imsi);
+	msgb_sgsap_lai_put(msg, lai);
+	if (new_id && new_id_len)
+		msgb_tlv_put(msg, SGSAP_IE_MOBILE_ID, new_id_len, new_id);
+	msgb_push_u8(msg, SGSAP_MSGT_LOC_UPD_ACK);
+	return msg;
+}
+
+/* 8.10 SGsAP-LOCATION-UPDATE-REJECT.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \param[in] rej_cause LU cause code, see also 3GPP TS 29.018, subclause 18.4.21.
+ *  \param[in] lai location area identifier.
+ *  \returns callee-allocated msgb with the encoded message */
+struct msgb *gsm29118_create_lu_rej(const char *imsi, uint8_t rej_cause, const struct osmo_location_area_id *lai)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, imsi);
+	msgb_tlv_put(msg, SGSAP_IE_REJECT_CAUSE, 1, &rej_cause);
+	if (lai)
+		msgb_sgsap_lai_put(msg, lai);
+	msgb_push_u8(msg, SGSAP_MSGT_LOC_UPD_REJ);
+	return msg;
+}
+
+/* 8.12 SGsAP-MM-INFORMATION-REQUEST.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \param[in] mm_info MM information, see also 3GPP TS 29.018, subclause 18.4.16.
+ *  \param[in] mm_info_len length of \a mm_info in octets.
+ *  \returns callee-allocated msgb with the encoded message. */
+struct msgb *gsm29118_create_mm_info_req(const char *imsi, const uint8_t *mm_info, uint8_t mm_info_len)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, imsi);
+	msgb_tlv_put(msg, SGSAP_IE_MM_INFO, mm_info_len, mm_info);
+	msgb_push_u8(msg, SGSAP_MSGT_MM_INFO_REQ);
+	return msg;
+}
+
+/* 8.14 SGsAP-PAGING-REQUEST.
+ *  \param[in] params user provided memory with message contents to encode.
+ *  \returns callee-allocated msgb with the encoded message or NULL on error. */
+struct msgb *gsm29118_create_paging_req(struct gsm29118_paging_req *params)
+{
+	int rc;
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, params->imsi);
+	rc = msgb_sgsap_name_put(msg, SGSAP_IE_VLR_NAME, params->vlr_name);
+	if (rc < 0)
+		goto error;
+	msgb_tlv_put(msg, SGSAP_IE_SERVICE_INDICATOR, 1, &params->serv_ind);
+	if (params->lai_present)
+		msgb_sgsap_lai_put(msg, &params->lai);
+	msgb_push_u8(msg, SGSAP_MSGT_PAGING_REQ);
+	return msg;
+error:
+	msgb_free(msg);
+	return NULL;
+}
+
+/* 8.15 SGsAP-RESET-ACK.
+ *  \param[in] params user provided memory with message contents to encode.
+ *  \returns callee-allocated msgb with the encoded message or NULL on error. */
+struct msgb *gsm29118_create_reset_ack(struct gsm29118_reset_msg *params)
+{
+	int rc;
+	struct msgb *msg = gsm29118_msgb_alloc();
+	if (params->vlr_name_present && params->mme_name_present == false)
+		rc = msgb_sgsap_name_put(msg, SGSAP_IE_VLR_NAME, params->vlr_name);
+	else if (params->mme_name_present && params->vlr_name_present == false)
+		rc = msgb_sgsap_name_put(msg, SGSAP_IE_MME_NAME, params->mme_name);
+	else
+		goto error;
+	if (rc < 0)
+		goto error;
+	msgb_push_u8(msg, SGSAP_MSGT_RESET_ACK);
+	return msg;
+error:
+	msgb_free(msg);
+	return NULL;
+}
+
+/* 8.16 SGsAP-RESET-INDICATION.
+ *  \param[in] params user provided memory with message contents to encode.
+ *  \returns callee-allocated msgb with the encoded message or NULL on error. */
+struct msgb *gsm29118_create_reset_ind(struct gsm29118_reset_msg *params)
+{
+	int rc;
+	struct msgb *msg = gsm29118_msgb_alloc();
+	if (params->vlr_name_present && params->mme_name_present == false)
+		rc = msgb_sgsap_name_put(msg, SGSAP_IE_VLR_NAME, params->vlr_name);
+	else if (params->mme_name_present && params->vlr_name_present == false)
+		rc = msgb_sgsap_name_put(msg, SGSAP_IE_MME_NAME, params->mme_name);
+	else
+		goto error;
+	if (rc < 0)
+		goto error;
+	msgb_push_u8(msg, SGSAP_MSGT_RESET_IND);
+	return msg;
+error:
+	msgb_free(msg);
+	return NULL;
+}
+
+/* 8.18 SGsAP-STATUS.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \param[in] cause sgs related cause code.
+ *  \param[in] err_msg user provided message buffer containing the errornous message.
+ *  \returns callee-allocated msgb with the encoded message */
+struct msgb *gsm29118_create_status(const char *imsi, enum sgsap_sgs_cause cause, const struct msgb *err_msg)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	uint8_t c8 = cause;
+	unsigned int err_msg_len;
+	msgb_tlv_put(msg, SGSAP_IE_SGS_CAUSE, 1, &c8);
+	if (imsi)
+		msgb_sgsap_imsi_put(msg, imsi);
+	if (err_msg) {
+		err_msg_len = msgb_l2len(err_msg);
+		if (err_msg_len > 255)
+			err_msg_len = 255;
+		msgb_tlv_put(msg, SGSAP_IE_ERR_MSG, err_msg_len, msgb_l2(err_msg));
+	}
+	msgb_push_u8(msg, SGSAP_MSGT_STATUS);
+	return msg;
+}
+
+/* 8.23 SGsAP-RELEASE-REQUEST.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \param[in] cause sgs related cause code.
+ *  \returns callee-allocated msgb with the encoded message. */
+struct msgb *gsm29118_create_release_req(const char *imsi, const uint8_t sgs_cause)
+{
+	struct msgb *msg = gsm29118_msgb_alloc();
+	msgb_sgsap_imsi_put(msg, imsi);
+	if (sgs_cause)
+		msgb_tlv_put(msg, SGSAP_IE_SGS_CAUSE, 1, &sgs_cause);
+	msgb_push_u8(msg, SGSAP_MSGT_RELEASE_REQ);
+	return msg;
+}
+
+/* 8.24 SGsAP-SERVICE-ABORT-REQUEST.
+ *  \param[in] imsi IMSI of the subscriber.
+ *  \returns callee-allocated msgb with the encoded message. */
+struct msgb *gsm29118_create_service_abort_req(const char *imsi)
+{
+	return create_simple_msg(SGSAP_MSGT_SERVICE_ABORT_REQ, imsi);
+}
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 04a98267..e9a9e4f2 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -219,6 +219,21 @@ gsm0808_lcls_config_names;
 gsm0808_lcls_control_names;
 gsm0808_lcls_status_names;
 
+gsm29118_msgb_alloc;
+gsm29118_create_alert_req;
+gsm29118_create_dl_ud;
+gsm29118_create_eps_det_ack;
+gsm29118_create_imsi_det_ack;
+gsm29118_create_lu_ack;
+gsm29118_create_lu_rej;
+gsm29118_create_mm_info_req;
+gsm29118_create_paging_req;
+gsm29118_create_reset_ack;
+gsm29118_create_reset_ind;
+gsm29118_create_status;
+gsm29118_create_release_req;
+gsm29118_create_service_abort_req;
+
 gsm0858_rsl_ul_meas_enc;
 
 gsm338_get_sms_alphabet;